Inflammatory bowel disease (IBD) is a group of chronic, relapsing and remitting inflammatory conditions that affect individuals throughout the life. Although the status of IBD as a canonical autoimmune disease has risen steadily by accumulated studies, it is not known whether the intestinal epithelial cell-derived proteins are involved in the pathogenesis of IBD. Recently, we have identified a mammalian lectin, galectin-4, as a colonic epithelial cell-derived pathogenic mediator in the exacerbation of colitis by using serological analysis of recombinant cDNA expression libraries (SEREX) in which cDNA libraries generated from colonic epithelial cells from T cell receptor alpha knockout (TCRalpha KO) mice were screened by using purified immunoglobulins from the TCRalpha KO mice. This discovery provides us a great opportunity to more closely examine the role of self-lectin originating from colonic epithelial cells in the pathogenesis of colitis. Based on our preliminary studies, we hypothesize that the colonic epithelial cell-derived galectin-4 contributes to the exacerbation of colitis by cross-linking the specific glycoreceptors and stimulating interleukin (IL)-6 production by the pathogenic T cells. In this application, we will initially plan to define our hypothesis by administration of recombinant galectin-4 into chronic colitis prone mice. We also plan to examine the therapeutic beneficial of in rive neutralization of galectin-4 activity on the chronic colitis by administration of galectin-4-specific monoclonal antibodies. In addition, the characteristic of galectin- 4/pathogenic T cell interaction and the involvement of immunological synapse and alpha2,3-sialyltransferase-I in galectin-4-induced IL-6 expression will be examined. These studies will not only enhance understanding of the pathogenic mechanisms of IBD but also provide important information to develop new therapeutic approaches for human IBD.